The present disclosure relates to a multilayer tactile sensor and a corresponding manufacturing method for such a sensor.
Generic multilayer tactile sensors are known as so-called pressure mats. Pressure mats are two-dimensional sensors with a pressure-sensitive surface that respond to a mechanical load. If for example a person steps on the active surface, the resulting mechanical load is detected and evaluated by a control unit connected to the sensor and converted into a corresponding reaction. A reaction to said event could for instance be turning off a technical system or displaying a warning message.
Known pressure mats are based on the principle that two layers with conductive electrodes are separated by a pressure-sensitive intermediate layer. An electrical property between the electrodes changes if the intermediate layer is compressed. The intermediate layer may comprise compressible elements for this purpose, so that, when pressure is directed transversely to the surface of the pressure mat, the two electrodes are pressed together and the electrodes get into direct contact between the compressible elements.
Alternatively, the intermediate layer can also be made of a material that changes its electrical resistance under pressure. Such an intermediate layer can be a continuous layer, so that even if the two electrodes do not come into direct contact with each other, said change of resistance can be detected using a suitable analysis circuit.
Based on the aforementioned basic principles, it is usually an aim to produce a very large sensor in one piece. For this the individual layers are first produced separately and are assembled to form the actual sensor in a subsequent step. In addition to a continuous intermediate layer, the electrodes may preferably also be configured as a continuous sheet, for example as a textile sheet with electrodes sewn or woven in. In this case, the sensor is formed by laying the individual layers on top of each other and fixing them together. Usually, this is achieved by placing the layers in a housing or laminating them into a composite. Both methods usually restrict the flexibility, in particular the pliability, of the sensor.
Whereas the loss of flexibility is initially insignificant if the sensor is used as a pressure mat, it is desirable for other applications to maintain the original flexibility of the individual layers. Such applications are for example the use of the tactile sensor as a robot skin, when the active surface of the sensor is adapted to the external contour of a robot or in cases in which the sensor is used as a pinch protection means on pinch and shear edges and the sensor being strip-shaped and extending along the edge to be monitored. In both cases, it is desirable to maintain the original flexibility of the individual layers as far as possible.